(1) Field of the Invention
The invention relates generally to the field of systems and more particularly to system that assesses the accuracy of assumed models of physical phenomena and provides alternate model selections in connection with information concerning the model, in the presence of noise in connection with the information. In a preferred embodiment, the invention facilitates selection of the physical processes relating to motion of a signal source moving in a medium, the propagation of the signal through the medium and the interception of the signal by the sensors being in response to received signals which may be corrupted by noise.
(2) Description of the Prior Art
Expert systems can be used to identify likely models of physical phenomena in response to information about the state of the phenomena, particularly where the information is corrupted by noise. The above-identified Baylog, et al., and Ferkinhoff, et al., I are articles which generally describe a system which is used to model the motion of an object through a fluid in response to information which is received by arrays of acoustic sensors placed in the fluid. The acoustic sensors receive acoustic signals which arise from motion of the object through the fluid, or which may be emitted by the object as it propels itself through the fluid. The particular types-of sensors in the array may be selected to detect certain types of information. For example, sensors may be selected to provide the azimuth bearing of the object relative to the sensor, the angle of depression or elevation of the object relative to the location of the sensor, and the frequency of the signal. Information from these sensors may be used to provide evidence to support models representing the motion of the object through the fluid.
One problem that arises in determining the likelihood that particular models accurately represent physical processes, including the motion of the target object, is that the sensors are likely to receive not only the signals as generated by the moving physical process or object, but also noise. Indeed, noise may be due not only to acoustic signals generated by other objects than the one being modeled, but also by reflections of the signals being generated by the object being modeled off of discontinuities in the fluid, such as off the ocean floor or surface, resulting in multi-path distortion. Depending on the relative levels of the signals and the noise, certain features which are present in the signals which are used to make the determination may be masked by the noise, or at least their detection may be difficult.